Laboratory, 4th Edition
Erin C. Amerman
Practical Lab-Style Test Bank
Questions | Detailed Rationales
SECTION 1: MICROSCOPE & LABORATORY TECHNIQUE
(Questions 1-15)
Question 1
When first focusing a specimen using the scanning objective (4x), which
focusing knob should be used?
A. Fine adjustment knob only
B. Coarse adjustment knob, then fine adjustment knob
,C. Diaphragm adjustment
D. Objective lens only
Correct Answer: B
Rationale: When starting with the lowest power objective (4x), the coarse
adjustment knob is used first to bring the specimen into approximate focus,
then the fine adjustment knob is used for precise focus. Using the coarse
adjustment knob on higher powers risks crashing the objective into the slide.
The diaphragm (C) controls light, not focus.
Question 2
What is the total magnification when using a 10x ocular lens and a 40x
objective lens?
A. 50x
B. 400x
C. 4x
D. 4000x
Correct Answer: B
Rationale: Total magnification is calculated by multiplying the ocular lens
magnification by the objective lens magnification. 10 × 40 = 400x. The ocular
lens is typically 10x, so total magnification = 10x × objective magnification.
, Question 3
Which objective lens requires the use of immersion oil to function properly?
A. 4x
B. 10x
C. 40x
D. 100x
Correct Answer: D
Rationale: The 100x (oil immersion) objective requires immersion oil to
reduce light refraction and increase resolution. Oil has the same refractive
index as glass, preventing light scatter and allowing more light to enter the
objective. Lower power objectives (4x, 10x, 40x) do not require oil.
Question 4
When preparing a wet mount slide, what is the purpose of adding a coverslip
at a 45-degree angle?
A. To prevent air bubbles
B. To stain the specimen
C. To magnify the specimen
D. To protect the objective lens
Correct Answer: A
Rationale: Placing the coverslip at a 45-degree angle and lowering it slowly
helps prevent air bubbles from forming under the coverslip. Air bubbles can